1. Field of the Invention
This invention relates to SiC-Al.sub.2 O.sub.3 composite sintered bodies and a method of producing the same, and more particularly to SiC-Al.sub.2 O.sub.3 composite sintered bodies suitable for use in structural materials having high strength and toughness and a method of producing the same.
2. Related Art Statement
Al.sub.2 O.sub.3 is widely used as a substrate or a package for integrated circuit, a chip for cutting tools or a refractory material. However, the strength and toughness of Al.sub.2 O.sub.3 are low as compared with those of a silicon nitride sintered body, so that there is a restriction in its use as a structural material for engine parts and the like.
The strength and toughness of Al.sub.2 O.sub.3 can be increased by dispersing SiC particles or SiC whiskers into the Al.sub.2 O.sub.3. For example, the increase of the toughness in the Al.sub.2 O.sub.3 sintered body through the dispersion of SiC whisker is disclosed in American Ceramic Society Bulletin, 64 [2], 298-304 (1985). Furthermore, Japanese Patent laid open No. 59-3,766 discloses the increase of the toughness in the Al.sub.2 O.sub.3 sintered body having an entangled microstructure of SiC and Al.sub.2 O.sub.3 and high strength and toughness. In the microstructure of these sintered bodies, SiC is liable to be a continuous phase, so that when the sintered body is heated in air, the oxidation of SiC is violent and the strength lowers, and the use of the sintered body can not be used at high temperatures for a long time.
Furthermore, the increase of the strength, toughness and hardness in the Al.sub.2 O.sub.3 sintered body through the dispersion of SiC particles is disclosed in Japanese Patent laid open No. 61-21,964 and No. 61-174,165. In these sintered bodies, however, SiC particles are mainly existent at the grain boundary of Al.sub.2 O.sub.3 grains constituting as a matrix, so that sufficient increase of the strength or toughness can not be attained in the Al.sub.2 O.sub.3 sintered body causing intergranular breakage during the breaking.